Recent emphasis on age-related morbidity addresses the increasing life expectancy of Western countries. Osteopenia is a multi-factorial process affecting a sizeable number of elderly individuals, with bone fractures producing significant morbidity and related mortality. A non-human primate would be a very useful experimental model for the study of age-related osteopenia, if it could be shown that it is similarly afflicted by age and if non-invasive methods utilized among humans could give a valid estimation of bone mineral content in the animal. Our previous studies utilizing SPA (single-photon absorptiometry) suggest age-related decrease in BMC (bone mineral content) among rhesus macaque skeletons, similar to that observed in humans. The present studies were done in order to further validate the utilization of bone densitometry (SPA) in the rhesus macaque, comparing their BMC and bone density (BD) with the size and weight of their corresponding bones. Both radii and the right femur of 102 adult rhesus monkey skeletons (5 to 23 years old), were obtained from the Caribbean Primate Research Center (CPRC) Skeletal Collection. There were 55 females and 47 males. Bone parameters were obtained using a Norland Digital Bone Densitometer, model 2780 at 2 scanning sites: distal 1/3 of radii and proximal 1/3 of femurs. Bone lengths (cm) and weights (gm) were compared and correlated with densitometric parameters. Excellent correlations were consistently found, with r values 0.74 to 0.96 and p less than 0.0001. Thus it appears that SPA at distal 1/3 radius or proximal 1/3 femur are a valid estimate of total bone mineral mass in rhesus monkeys.